A method of producing 1,1,3,3,3-pentafluoropropene

Abstract: A method is proposed of producing 1,1,3,3,3-pentafluoropropene, in which 1,1,1,3,3-pentafluoro-2,3-dichloropropane is dechlorinated by using hydrogen in the presence of a metal oxide catalyst. Based on this production method, 1,1,3,3,3-pentafluoropropene can thus be produced with high yield rates.

Description: Industrial use This invention relates to a method of producing 1,1,3,3,3-pentafluoropropene which can be easily changed to 1,1,1,3,3-pentafluoropropane by hydrogenation and which is useful as an intermediate in the production of other fluorine-containing organic compounds as well as a monomer to produce high molecular compounds. Prior art As a production method of 1,1,1,3,3-pentafluoropropane, it is known that 2,2,3-trichloro-1,1,1,3,3-pentafluoropropane is reduced by hydrogen by using a palladium catalyst (U.S. Patent No.2942036). The known method, however, is not suitable for producing 1,1,1,3,3-pentafluoropropane industrially because the yield of the product is low due to the formation of a large amount of 1,1,3,3,3-pentafluoropropene and 2-chloro-1,1,3,3,3-pentafluoropropene as byproducts. Another method is also known in which 1,1,3,3,3-pentafluoropropene is reduced by hydrogen at room temperature by using a palladium catalyst carried on alumina (Bull. Acad. Sci. USSR Div. Chem. Sci. (Eng.Transl.) 1312 (1960)). In this known method, however, the yield of the target product of 1,1,1,3,3-pentafluoropropane is as low as about 70 percent. 1,1,3,3,3-pentafluoropropene is a useful compound which can be used as a raw material in producing various kinds of resins and as an intermediate in producing some medicines or agricultural chemicals, as well as a raw material of HFC blowing agents which do not destroy the ozone layer. So far it is known that 1,1,3,3,3-pentafluoropropene can be synthesized by dehydrochlorination of 1,1,1,3,3-pentafluoro-3-chloropropane with a base (J. Am. Chem. Soc., 68 496(1946)). In this known reaction, however, it is difficult to obtain the raw material and there are many problems in using the reaction industrially as a synthetic method of producing 1,1,3,3,3-pentafluoropropene. Further, there is a known method of using decarboxylation of a potassium salt of α-hydroperfluoroisobythylate. In this method, however, it is difficult to obtain the raw material and it is difficult to use the decarboxylation reaction itself industrially (Synthesis of Fluoroorganic Compounds, I. L. Knunyants and G. G. Yakobson, Springer-Verlag, Berlin, Heidelberg, p.8 (1985)). Besides, there is also a known method of using dehydroiodination of 3-iodo-1,1,1,3,3-pentafluoropropane, but again, it is difficult to obtain a large amount of the raw material at low cost (do., Synthesis of Fluoroorganic Compounds). U.S. Patent 2,942,036 relates to the hydrogenation of 1,2,2-trichloropentafluoropropane at temperatures in the range of 175-350°C and in the presence of palladium-activated carbon catalyst, in order to obtain 1,2,2-trihydropentafluoropropane. U.S. Patent 2,900,423 discloses the manufacture of perfluoropropene by dechlorinating 1,1,1,2,3,3,3-heptafluoro-2-chloropropane by using hydrogen in the presence of a metal oxide catalyst. Object of invention It is an object of this invention to provide a production method which is industrially feasible and easy to produce 1,1,3,3,3-pentafluoropropene by using 1,1,1,3,3-pentafluoro-2,3-dichloropropane as a raw material. Constitution of invention After studying processes of producing 1,1,3,3,3-pentafluoropropene effectively and at low cost, the inventors found a process in which 1,1,3,3,3-pentafluoropropene is derived with a high selectivity from 1,1,1,3,3-pentafluoro-2,3-dichloropropane which is available at low cost, resulting in the present invention. That is, the present invention relates to a method of producing 1,1,3,3,3-pentafluoropropene by dechlorinating 1,1,1,3,3-pentafluoro-2,3-dichloropropane with hydrogen in the presence of a metal oxide catalyst. In the invention, the raw material 1,1,1,3,3-pentafluoro-2,3-dichloropropane can be easily obtained by fluorinating hexachloropropene with HF in the presence of antimony halide. In the reductive dehalogenation of 1,1,1,3,3-pentafluoro-2,3-dichloropropane according to the invention, the metal oxide to be used as a catalyst is preferably an oxide of at least one metal selected from iron, chromium, cobalt, copper, nickel and manganese. The metal oxide catalyst can be obtained by burning a metal hydroxide, which is precipitated by adding an alkali of aqueous ammonia or an alkali metal hydroxide in an ordinary way to an aqueous solution of a chloride, sulfate or nitrate of a metal such as chromium, iron, cobalt, copper, nickel and manganese. These metal oxide catalysts can be used alone, but a multiple oxide of several metals selected from the said metals and a mixture of several metal oxides can also be used in the reaction. These metal oxide catalysts can be used in the pressed form of granules or pellets. It is also acceptable for the catalyst to be carried on a carrier which does not participate in the reaction, for example, at least one kind of carrier selected from active carbon, alumina, aluminum fluoride, silica gel and calcium fluoride. These metal oxides are allowed to have zero valence by pretreatment with hydrogen or reduction during the reaction. As for the excess amount of hydrogen, though the reaction can be carried out when the mole ratio of hydrogen to the necessary raw material is 1 or more, in practice a ratio of 1.5 mole or more is preferable. Because excessive hydrogen reduces the contact time and reduces the conversion yield, a mole ratio of about 2 to 5 is used in practice. The reaction temperature in the reductive dehalogenation is desirably from 200°C to 400°C and can be selected properly depending on the activity of the catalyst. As the velocity of the reaction is well-known to be increased by raising the reaction temperature, a high reaction temperature is needed when using a catalyst of low activity. But when the temperature is over 400°C, the ratio of C2 and C4 compounds, which are thought to be formed by the breaking and bonding of C-C bonds, is increased to lower the selectivity. The contact time can be properly selected depending on the conversion yield set by the catalyst activity and the reaction temperature. Generally, when catalyst activity is low, the proper conversion yield can be set by extending the contact time. Industrial potential of the invention According to the invention, 1,1,3,3,3-pentafluoropropene can be produced with a good selectivity because 1,1,1,3,3-pentafluoro-2,3-dichloropropane is dechlorinated with hydrogen in the presence of a metal oxide catalyst. The 1,1,3,3,3-pentafluoropropene can be changed to 1,1,1,3,3-pentafluoropropane by reaction with hydrogen in a gas phase in the presence of a palladium catalyst A product of this invention, 1,1,3,3,3-pentafluoropropene, can be easily changed to 1,1,1,3,3-pentafluoropropane by hydrogenation and is a useful compound as an intermediate in the production of other fluorine-containing organic compounds as well as a monomer to produce high molecular compounds. Examples This invention is explained in more detail through the following examples. Example 1 120 g of Cr(NO 3 ) 3 · 9H 2 O was dissolved in 250 ml of water. The solution, being agitated with 200 ml of 28% aqueous solution of ammonium hydroxide, was added to 400 cc of heated water to precipitate the hydroxide. After being filtered, washed with pure water and dried, the precipitate was burnt at 450°C for 5 hours to yield the powder of an oxide (chromium oxide). The powder was molded to a cylindrical form of 5 mm in diameter and 5 mm in height using a tapping mold machine. 10 g of the said chromium oxide powder was filled into a reactor tube made of Hastelloy C (Φ 20 mm x 1000 mm). After the reactor was set at the reaction temperature, pretreatment was carried out in advance by passing hydrogen into the reactor at the rate of 200 ml/min for 3 hours. Then, 1,1,1,3,3-pentafluoro-2,3-dichloropropane was introduced into the reactor at the rate of 50 ml/min. The produced gas was analyzed by gas chromatography after being washed with water. The selectivity and conversion yield were calculated by multiplying areas of peaks in the gas chromatography analysis by correction factors determined separately. The results are shown in Table 1. Reaction temperature Conversion Selectivity 300°C 20% 96% 350°C 48% 95% 400°C 72% 94% Though a main by-product was 1,1,1,3-tetrafluoro-3-chloropropene, it was proved that the target product (1,1,3,3,3-pentafluoropropene) can be obtained with high selectivity when the reaction is carried out based on the method of the third invention. Example 2 The reaction was carried out in the same way as Example 1 except that a multiple oxide of copper and chromium was used as the catalyst. The results are shown in Table 2. Reaction temperature Conversion Selectivity 300°C 35% 87% 350°C 52% 85% 400°C 84% 82% Though a main by-product was 1,1,1,3-tetrafluoro-3-chloropropene, the target product was obtained with high selectivity also in this example. Example 3 The reaction was carried out in the same way as Example 1 except that an oxide of iron was used as the catalyst. The results are shown in Table 3. Reaction temperature Conversion Selectivity 300°C 18% 89% 350°C 33% 86% 400°C 68% 78% Though a main byproduct was 1,1,1,3-tetrafluoro-3-chloropropene, the target product was obtained with high selectivity also in this example. Example 4 87 g of Ni(NO 3 ) 2 · 6H 2 O was dissolved in 250 ml of water. After adding 181 g of silica gel to the solution, the mixture was dried, then heated to 400°C to yield nickel oxide. The oxide was molded to a cylindrical form of 5 mm in diameter and 5 mm in height using a tapping mold machine. 10 g of the said catalyst was filled into a reactor tube (Φ 20 mm x 1000 mm) made of Hastelloy C. After the reactor was set at the reaction temperature, pretreatment was carried out in advance by passing hydrogen into the reactor at the rate of 200 ml/min for 3 hours. Then, 1,1,1,3,3-pentafluoro-2,3-dichloropropane was introduced into the reactor at the rate of 50 ml/min. The produced gas was analyzed by gas chromatography after being washed with water. Selectivity and conversion yield were calculated by multiplying areas of peaks in the gas chromatography analysis by correction factors determined separately. The results are shown in Table 4. Reaction temperature Conversion Selectivity 300°C 21% 92% 350°C 43% 85% 400°C 72% 82% Though a main by-product was 1,1,1,3-tetrafluoro-3-chloropropene, the target product was obtained with high selectivity also in this example. Example 5 120 g of Cr(NO 3 ) 3 · 9H 2 O was dissolved in 250 ml of water. After adding 181 g of silica gel to the solution, the mixture was dried, then heated to 400°C to yield oxide. The product was molded to a cylindrical form of 5 mm in diameter and 5 mm in height using a tapping mold machine. 10 g of the said catalyst was filled into a reactor tube (Φ 20 mm x 1000 mm) made of Hastelloy C. After the reactor was set at the reaction temperature, pretreatment was carried out in advance by passing hydrogen into the reactor at the rate of 200 ml/min for 3 hours. Then, 1,1,1,3,3-pentafluoro-2,3-dichloropropane was introduced into the reactor at the rate of 50 ml/min. The produced gas was analyzed by gas chromatography after being washed with water. Selectivity and conversion yield were calculated by multiplying areas of peaks in the gas chromatography analysis by correction factors determined separately. The results are shown in Table 5. Reaction temperature Conversion Selectivity 300°C 20% 98% 350°C 46% 96% 400°C 74% 95% Though a main byproduct was 1,1,1,3-tetrafluoro-3-chloropropene, the target product was obtained with high selectivity also in this example. Example 6 Potassium fluoride aqueous solution (5.4 moles) was added to calcium nitrate aqueous solution (2.7 moles). To the obtained slurry, copper nitrate (1 mole), nickel nitrate (1 mole) and chromium nitrate (1 mole) were added. Then, potassium hydroxide (0.1 mole) was added. The precipitated solid was filtered and dried, then heated to 400°C to yield an oxide. The product was molded to a cylindrical form of 5 mm in diameter and 5 mm in height using a tapping mold machine. 10 g of the said catalyst was filled into a reactor tube (Φ 20 mm x 1000 mm) made of Hastelloy C. After the reactor was set at the reaction temperature, pretreatment was carried out in advance by passing hydrogen into the reactor at the rate of 200 ml/min for 3 hours. Then, 1,1,1,3,3-pentafluoro-2,3-dichloropropane was introduced into the reactor at the rate of 50 ml/min. The produced gas was analyzed by gas chromatography after being washed with water. Selectivity and conversion yield were calculated by multiplying areas of peaks in the gas chromatography analysis by correction factors determined separately. The results are shown in Table 6. Reaction temperature Conversion Selectivity 300°C 35% 98% 350°C 82% 95% 400°C 91% 93% Though a main byproduct was 1,1,1,3-tetrafluoro-3-chloropropene, the target product was obtained with high selectivity also in this example.

Claims: A method of producing 1,1,3,3,3-pentafluoropropene that is characterized by dechlorinating 1,1,1,3,3-pentafluoro-2,3-dichloropropane by using hydrogen in the presence of a metal oxide catalyst. The production method as defined by Claim 1, in which the metal oxide catalyst to be used in the dechlorination reaction is an oxide of at least one metal selected from iron, chromium, cobalt, copper, nickel and manganese. The production method as defined by Claim 1 or 2, in which the metal oxide catalyst is carried on a carrier composed of at least one selected from active carbon, alumina, aluminum fluoride, calcium fluoride and silica gel. The production method as defined by any of Claims 1 to 3, in which the dechlorination reaction is carried out by using at least a stoichiometric amount of hydrogen. The production method as defined by any of Claims 1 to 4, in which the dechlorination reaction is carried out at a temperature between 200°C and 400°C.

Inventors: AOYAMA HIROKAZU, NAKADA TATSUO, SEKI EIJI, YAMAMOTO AKINORI, AOYAMA, HIROKAZU, NAKADA, TATSUO, SEKI, EIJI, YAMAMOTO, AKINORI, Aoyama, Hirokazu, c/o Daikin Industries Ltd., Nakada, Tatsuo, c/o Daikin Industries Ltd., Seki, Eiji, c/o Daikin Industries Ltd., Yamamoto, Akinori, c/o Daikin Industries Ltd.
Applicants: DAIKIN IND LTD, DAIKIN INDUSTRIES, LIMITED
Application year: 1994
Main classification: C07C17
IPC codes: C07C17